Quick grow info:
I’m using mother earth 70/30 coco perlite mix, fertilizers b52, voodoo juice, and ph perfect sensi grow. Lighting is 14 inches from top and on 24/0
Problem:
One of 4 plants top leaves are making a wide curl downwards, no dead tips, but leaves slightly yellow (top ones)
Picture of the problem in question
What strain is it and if it’s an auto-flower or photo plant. 4 possible problems are over watering, ph of water, tap water or underfed. @PreyBird1 and several others grow in coco so he can give you a better answer than I can.
I got the seeds off a buddy he forgot what stair but believes ak47 auto or gurilla glue auto
Also all the soil was from the same bag and ive used the same amount of ph perfect sensi grow, grow space did get a little cold though but it only dipped to 65
That just seems really dryyy. But looks can be deceiving
Try and give it some sleepy time.
The below the surface is still very damp
I asked if it was an auto because I have had auto’s start out looking like that. The yellowing leaves should turn green again in time. @TechDCo has good advice about sleepy time. Run your lights 18/6, just remember with auto’s anything like a light change will cause them to flower.
Try rasing the pot put a brick underneath to help air flow. I think some sleepy time 18/6 will be ok to try.
Ya right 
Autos can be difficult with light ya nevwr know when they’ll flower. Photoperiods can be worse with light changes.
Reason i decided 24/0 is my work schedule is chaotic and i dont have a autotimer on the lights
can you grow outside in season? your schedule my not work for growing inside 
Cheap mechanical timer bn-link around 10$ and ipower around 7$ on Amazon, run them 18/6. I’ve personally had better results with the dark period. Outside in nature they have a dark period unless you live somewhere where it’s light year round and strains of that region would be suited and accustomed to no dark. 18/6 is like a long summer day and they would do better all around . Just my experience, currently have an auto growing … a monster that’s a little over 4 foot tall and basically takes up 4x4 area in a tent and is grown at 18/6 
an Auto breeder at some other place told me that Auto do really well 20/4 for a light schedule
with a lower PPFD
